What is back billing?
Back billing is when your energy supplier asks you to pay for gas or electricity you have already used, because it did not charge you accurately at the time. It often arrives as a catch up bill, and the amount can be a shock.
Ofgem says a back bill can follow a billing mistake or a problem with your meter. The Energy Ombudsman adds that it can happen when a new meter reading shows earlier estimated readings were wrong.
Most of us file the bill and hope. That is the Do-Nothing Default, and with back billing it can cost you money you do not owe. This guide uses Ofgem’s advice on back bills and the Energy Ombudsman’s guide, both read on 5 November 2026.
What are the back billing rules?
Ofgem’s back billing rules mean you do not have to pay for energy you used more than 12 months ago in certain cases. Ofgem lists the three situations where the 12 month limit protects you.
- You have not had an accurate bill for that energy before.
- You have not been told what you needed to pay through a statement of account.
- Your Direct Debit amount was previously set too low to cover what you owed.
Ofgem says the back billing rules apply to households and microbusinesses. The Energy Ombudsman describes the effect in plain terms: the longest period you can be back billed for is one year back from the date on the new bill.
The Ombudsman also notes that the rule does not stop a supplier charging for older energy if you have been billed for the same amount before. If a charge repeats an earlier accurate bill, it is a different issue from back billing.
When can a supplier still back bill you?
Ofgem says you will have to pay for energy used more than 12 months ago if you have acted unreasonably. Ofgem gives three examples.
- Stopping your supplier from billing you accurately, including by blocking access to your meter.
- Ignoring requests for payment from your supplier.
- Stealing electricity or gas.
The Energy Ombudsman makes the same point and adds that you have a responsibility to make sure your supplier can get accurate readings. That does not mean every missed reading is unreasonable behaviour. Ofgem’s examples are about blocking, ignoring and stealing.
It is also worth separating two things. You still need to pay any accurate bill you are sent, including a back bill, according to Ofgem. The rules limit the period a back bill can cover, but they do not cancel a correct charge for recent energy.
Key takeaways
- Back billing rules cover households and microbusinesses.
- You may not have to pay for energy used more than 12 months ago, in the cases Ofgem lists.
- Blocking meter access or ignoring payment requests can remove that protection.
- Ask for a breakdown, and contact your supplier right away if you think the rules were not followed.
Why do back bills happen?
The Energy Ombudsman says suppliers rely on estimated readings when they cannot get an actual one from you or your meter. That is standard practice, and it is where most back billing starts.
It gives several reasons readings go missing. During the pandemic many meters went unread for over two years, and some first generation smart meters were faulty and had to be replaced. A home that is vacant or inaccessible can also stop the supplier reading the meter.
The Ombudsman adds that consumers have reported cases where a supplier’s system appears to have rejected an actual meter reading that did not fit the usual pattern. That is why a bill can use estimates even when you have given real readings.
It also says many people have reported recalculated bills that go back further than 12 months, even though the regulator says back billing should not occur. If that sounds like your bill, the steps below are the place to start.
What should you do if you get a back bill?
The Ombudsman sets out four steps, and they work well for any back bill.
First, check the billing dates. Look at the period the bill covers. It may be split into sections or show tariff changes, so if it is unclear, ask your supplier to explain how it was worked out.
Second, review the amount owed. Check the date on the bill and the earliest date it covers, and see if any deductions have been made. If the amount still seems too high, ask your supplier to review it.
Third, ask for a breakdown showing the meter readings and how the charges were calculated. That helps you see whether it is a back bill and whether any of it falls outside the 12 months.
Ofgem says you should contact your supplier right away if you think it has not followed the back billing rules. It says suppliers will refund any money taken in error, and that you can complain if they keep asking for payment for a period the rules cover.
Fourth, escalate if needed. The Ombudsman says that if the issue is not resolved within eight weeks, or you get a deadlock letter, you can contact it for a free, impartial review. Our Energy Ombudsman complaint guide explains that route.
How can you avoid a back billing surprise?
You cannot control your supplier’s systems, but you can leave a clear trail. Give a meter reading whenever you can, and keep the dates. Our guide to taking an energy meter reading correctly shows how.
A smart meter sends readings automatically, which reduces estimates. Our smart meter guide explains what to expect. Reading your bill each time also helps, because an estimate that looks wrong is easier to challenge early. Our guide to understanding your energy bill walks through each section.
Back billing is a billing problem, not a price problem. If you want to see what else is on offer for your home, a comparison takes a few minutes.
Frequently asked questions about back billing
- How far back can an energy supplier back bill you?
- Ofgem’s rules say you do not have to pay for energy used more than 12 months ago in the situations it lists, such as having had no accurate bill for it. The Energy Ombudsman describes this as one year back from the date on the new bill.
- Do back billing rules apply to businesses?
- Ofgem says the rules apply to households and microbusinesses. Larger businesses are not covered by that wording, so check your contract.
- Can a supplier back bill you if you block access to the meter?
- Yes. Ofgem says you will have to pay for energy used more than 12 months ago if you have acted unreasonably, for example by blocking access to your meter or ignoring requests for payment.
- Who do I complain to about a back bill?
- Contact your supplier first. The Energy Ombudsman says that if it is not resolved within eight weeks, or you get a deadlock letter, you can ask it for a free, impartial review.
Sources: Ofgem, What to do if you get a back bill and Energy Ombudsman, What is back billing? (published 16 June 2025), both read 5 November 2026.
